A centrifugal compressor utilizes rotors, also known as impellers, to impart to a fluid (typically air) the energy necessary to change the pressure of the fluid. The rotor of a common type of centrifugal compressor includes a number of blades, also known as vanes, disposed radially between a doughnut-shaped cap, also known as a shroud, and a circular base, also known as a hub. The blades, cap, and base of such a rotor are arranged to form fluid flow passages within the rotor that converge towards the center of the rotor.
When the above-described rotors are rotated at high speeds, they can generate high pressures and temperatures. These rotors preferably have high rotational and structural stability (e.g., strength, balance), high heat resistance, high efficiency, and also are relatively easy to manufacture. These design constraints are particularly significant as the size of the rotors increases, because the stresses on the rotors increase as the size of the rotors increases.
Attempts have been made to improve the dynamic performance of such rotors by changing the geometry and/or arrangement of the blades within the rotors. For example, U.S. Pat. No. 6,729,845 to Rossi discloses the use of curved blades within the rotor. Attempts have also been made to improve the methods of manufacturing such rotors. For example, U.S. Pat. No. 6,276,899 to Lambert et al. discloses a method of welding together rotor components; U.S. Pat. No. 6,976,828 to Godichon et al. discloses a method of bolting together rotor components; US 2002/0051707 to Takahashi et al. discloses a method of molding a rotor; and U.S. Pat. No. 7,305,762 to Mola and U.S. Pat. No. 6,676,826 to Battistini et al. disclose methods of machining a rotor. Notwithstanding these advances, further improvements in the design, construction, and overall performance of centrifugal compressor rotors are desirable.